Green engineering is defined as the design, commercialization, and use of processes and products that are feasible and economical while reducing the generation of pollution at the source and minimizing the risk to human health and the environment. Green engineering promotes sustainability in all engineering disciplines and practices, and incorporates development and implementation of technologically and economically viable products while adhering to the principles of green engineering. Green thermodynamics is a subcategory of green engineering related to energy. In thermodynamics, the concept of green can be associated with an energy source, an energy interaction or transfer, and energy conversion or use. An energy source that can be extracted and brought into a useful form with minimal adverse impact on the environment and the future supplies can be viewed as green. With this definition, clean, renewable and sustainable energies like solar, wind, geothermal, tidal, wave, and ocean thermal energies are green energies, but fossil fuels are not. Some forms of bioenergy that involve combustion are not quite green since it is renewable and sustainable, but not clean. Exergy destruction associated with energy transfer and energy conversion, and adverse effects on human health and the environment are measures of deviation from thermodynamic greenness. The starting point for making the incorporation of green engineering widespread in real-world engineering practice is education, and engineering courses should start incorporating green components. In this paper, green components of thermodynamics are identified, general aspects of green practices associated with thermodynamics are discussed, their impacts are assessed, and examples are presented. Extensions to other related areas of green engineering practices are made. It is hoped that this presentation will attract the attention to green aspects of thermodynamics, and will accelerate the generation, dissemination, and utilization of green ideas and practices. Copyright (0 2007 John Wiley & Sons, Ltd.